Certain items such as food and beverages are often sold and stored in product containers. In many instances, an inventory of content remaining in product containers is taken to determine the number of product containers to purchase. For example, a consumer periodically performs a visual check to inventory contents remaining in food and beverage containers to identify a shopping list of items to purchase from a grocery store. In another example, bar and restaurant operators periodically inventory the amount of alcohol left in bottles to determine the amount of alcohol sold and identify quantity and type of alcohol to be purchased/replenished. The inventory of content remaining in product containers has been traditionally determined manually. This manual process is often laborious, imprecise and error prone. For example, it is often difficult for a person to visually determine an amount of liquid beverage remaining in a bottle with precision in a reliable manner. In commercial settings, the amount of time spent by an employee to manually inventory the remaining content represents a real employment cost realized by the employer. Therefore, there exists a need for a better way to determine the amount of content remaining in a container.